The present invention relates to a method for image processing in a non-contact gauge measurement system, and more particularly, to a method for increasing the dynamic light intensity range of an image by combining or fusing data from multiple images collected at different levels of illumination to create a single floating-point representation of an object undergoing measurement.
Photogrametric measurement systems such as laser range finders, illuminate an object undergoing measurement using structured light. Reflections of the structured light projected on the surface of the object are captured by one or more calibrated cameras, generating images comprised of pixels. These are representative of the light intensity on illuminated portions of the object""s surface. In some applications, the structured light is in the form of a set of laser planes. Where the laser planes intersect the surface of the object, a striping effect is achieved. By detecting these laser light stripes in the images of the object""s surface, point correspondences can be established and triangulation techniques employed to digitally reconstruct a three-dimensional representation of the surface of the object.
The surface of many objects include regions which are shiny or dull, or otherwise have poor reflectivity characteristics. Structured light projected onto these surfaces can result in a high range of dynamic light intensity levels, i.e. dull spots and overly bright spots. This results in poor laser stripe identification in the resulting images obtained by the cameras. Furthermore, in some situations, entire image regions which are representative of portions of an object""s surface may become corrupted due to under exposure, i.e. the region appears black, or saturation, i.e. the region appears white.
When using photogrametric methods to identify or measure objects in an image, the accuracy with which a salient feature in the image is located is negatively impacted by pixel saturation or pixel noise. Therefore, to view a scene which has a high dynamic range of illumination intensity, i.e. from dark to light, inexpensive low dynamic range cameras often prove inadequate. But, in some applications, the use of expensive, high dynamic range cameras is not possible.
Accordingly, there is a need in the industry for a method of utilizing lower performance and lower cost cameras, having lower dynamic light ranges, to provide high dynamic light range images.
Briefly stated, the present invention provides a method for increasing the dynamic light intensity range of an image by fusing pixel data from multiple images collected at different levels of illumination to create a single floating-point image representation of an object undergoing measurement.
In one embodiment, the present invention provides a method of establishing the location of features in an image by preventing illumination saturation of individual pixels comprising the image. In another embodiment, the present invention extends the dynamic illumination range of an imaging system by generating a high dynamic illumination range floating-point representation of the image.